1. Field of the Invention
The present invention relates to a process for manufacturing a printed wiring board and in particular to a process for manufacturing a multilayer printed wiring board.
2. Prior Art
A multilayer printed wiring board has found in variety of electronic equipment, such as computers, electronic switching system or the like.
Prior art process for manufacturing a multilayer printed wiring board comprises the steps of: disposing an internal printed wiring board comprising an insulating plate and circuit patterns provided on one or both surfaces thereof and prepreg sheets so that the internal printed wiring board is sandwiched between the prepreg sheets; disposing external boards having a copper foil on the outermost surface thereof so that the internal printed wiring board and prepreg sheets are sandwiched between the external printed wiring boards; bonding resulting structure under pressure; forming through-holes through the resulting laminated structure; then forming through holes or copper plated-through hole and circuit patterns for external boards by using the tenting process or the additive process, etc.; and thereafter performing application of a solder resist film and finish treatment.
There has been a demand to avoid the use of organic solvents in the process for manufacturing printed wiring boards in order to preserve global environment.
However, a resist film which is soluble to organic solvents has to be used as an additive mask since used additive plating liquid is highly alkaline in the prior art process for manufacturing printed wiring boards. There has been a problem that an organic solvent is required in the manufacturing process.